Vacuum can be a source of motive force for actuators of a vehicle. Vacuum may be provided via an intake manifold of an engine or via a vacuum pump. In some vehicle vacuum systems, vacuum may be provided by both a vacuum pump and an intake manifold of an engine so that there may be sufficient vacuum during periods of vacuum demand. However, it may be difficult to determine if there are leaks within the vacuum system during vehicle operation when vacuum is being consumed. Further, since barometric pressure can vary with altitude and weather, it may be difficult to establish a vacuum leak rates under various environmental conditions.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for assessing vacuum system degradation for a vehicle, comprising: operating a vacuum pump during a condition of substantially no vacuum consumption via vacuum consumers of the vehicle; and providing an indication of vacuum degradation for the vehicle via a single vacuum leak threshold, the single leak threshold referenced to a leak rate at a plurality of altitudes.
By limiting consumption of vacuum from a vacuum system, it may be possible to accurately determine a vacuum leak rate of a vacuum system during vehicle operation. In particular, vacuum consumption by vehicle systems can be limited so as to increase a signal to noise ratio of vacuum leaks within a vacuum system. Further, it may be desirable to establish a single leak threshold that is applicable whether the vacuum system is at sea level or at some higher altitude. For example, a vacuum leak detection method may be structured to compensate for barometric pressure so as to be less sensitive to changes in atmospheric pressure allowing vacuum leak rates to be compared to a single leak rate threshold.
The present description may provide several advantages. For example, the approach may simplify vacuum leak diagnostic calibration and thereby reduce system cost. Further, the approach may reduce a number of pressure sensors for diagnosing vacuum leaks in a vacuum system. Further still, the approach may improve the reliability of diagnosing vacuum leaks.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.